There are many designs of electrical sauna heaters that use heating elements. GB645279A discloses a sauna heater that is heated by a fire as which means that the heating plate comprised of three concentrically arranged annular pieces and a disc shaped piece must withstand flames and smoke. There is no disclosure of passage of air from the heat chamber to the rocks.
The majority of designs comprise several electrical heating elements with sauna rocks placed on top of or in around the elements. The contact between the rocks and the elements cause damage to both components and they quickly deteriorate. Common practice amongst sauna users is the pouring of water onto the rocks. This is done to increase the apparent heat in the sauna cabin by raising the humidity. Pouring water onto the rocks and elements adds to the rate of deterioration. In many of these designs, it is only the rocks that protect the user from direct contact with the heating elements and as the rocks break down from use the elements become exposed causing a hazard to safety. For example, although DE2300293A1 discloses a series of air outlet openings for hot air provided at the upper edge of an inner lateral boundary of tray holding coals. this would allow the admittance of water.
In some designs the issue of safety has been addressed by placing protective shields over the elements. This has the effect of reducing the heat being transferred to the rocks. It then becomes difficult to raise the humidity of the sauna cabin.
JP2010142374A discloses a relatively complex environment within the heater body having a series of trays between a heater and a perforated plate. The hottest place within the heater will be just above the heater elements, and the coolest place within the heater will be directly below the perforated plate. In this disclosure there is a considerable distance between the two. As the perforated plate is constantly being cooled by the pouring on of water, the water that is not evaporated enters through the perforated plate into the environment of the heater housing and is retained there in the channels that are attached to the inside of the heater shell. The water will evaporate to increase the humidity within the heater shell. 100% humidity is likely in this environment. At 100% humidity a dew point of 100 deg C. is possible. Since the perforated plate is being constantly cooled by water the temperature of the plate is like to be 100 C. therefore condensation could occur on the underside of the plate and drip back down into the trays. This will prevent the heating of the rocks and cause poor air circulation. Poor air circulation will also have an adverse effect on the heating elements. Also the proposed perforated tray will not provide sufficient air passage.
The present invention addresses these issues, improving operating and maintenance issues associated with electric sauna heaters, and improving safety in use. In particular, the present invention avoids problems associated with a build-up of humidity within the apparatus.